Question

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1. Light coming from slit S₁ makes distance r₁to the screen. Light coming from slit S₂ makes distance r₂ to the screen. If the wave length is l, for the constructive interference r₁ – r₂have to be equal to

Bright fringe S o S,

1. 3l;
2. l;
3. 3l/2;
4. l/2;
5. A and B;
6. C and D.

Answer 1

For constructive interfernece, the path difference ( r₁ - r₂) is an even multiple of (0.5* wavelength) i.e. even multiple of (l / 2) .

( r₁ - r₂) = (2m) * ( l /2) = ( m* l) where m = 0, 1, 2, 3, .......

For constructive interference, ( r₁ - r₂) = l ;  ( r₁ - r₂) = 3l .

Option (A) and Option (B) both are correct.

Correct choice: (E)